Unintegrated DNAs of baboon endogenous leukemia virus have been purified from recently infected cells. The circular viral DNAs and linear viral DNAs have been separated and characterized with respect to their buoyant density and electrophoretic mobility. These unintegrated viral DNAs are biologically active in that they are infectious. Restriction endonuclease screening provided enzymes that make no cut, one, two and multiple cuts. Using these enzymes, a tentative restriction map of baboon viral DNA is constructed. High molecular weight DNAs prepared from exogenously infected cells is transfectable in dog and human cells. DNAs similarly prepared from baboon tissues, however, have not yet yielded detectable virus although the tissue has the entire information for virus production.